Work vehicles such as agricultural combines monitor a variety of drive parameters. They have a variety of sensors responsive to pressures, speeds and positions of the various components that comprise the drive system.
For example, a sensor may directly indicate the gear ratio or gear range of a gearbox in the drive system. Other sensors may measure different parameters, such as hydraulic pressure, rotational speed, and other parameters.
In some vehicles, system parameters such as gear ratios may not be sensed directly, but may be determined by combining sensor data and knowledge of the mathematical system model to calculate or otherwise determine these system parameters.
An example of such a system is disclosed in the assignee's co-pending U.S. patent application Ser. No. 10/167,310 (“310 application”) filed Jun. 11, 2002, for a “COMBINE HAVING A SYSTEM ESTIMATOR TO AUTOMATICALLY ESTIMATE AND DYNAMICALLY CHANGE A TARGET CONTROL PARAMETER IN A CONTROL ALGORITHM”. In this application, a gear ratio is determined by an electronic controller coupled to a motor speed sensor and a rotor speed sensor. By monitoring a gearbox input speed (the motor) and a gearbox output speed (the rotor) the system of the '310 application is able to determine the selected gearbox gear ratio indirectly.
The system and method of the '310 application is not without limitations. It is predicated on accurately calculating the speed range during an initial 1.3 second hydrostatic rotor acceleration phase. It also requires correct operation of the motor speed sensor. Should the motor sensor fail, the system may not be able to accurately determine the gear ratio.
It is an object of this invention to provide an improved system and method for determining the gear ratio of a gearbox.
It is also an object of this invention to provide for a redundant method to determine gearbox ratios.